Method of manufacturing commutators for small-size electric machines

ABSTRACT

A method of manufacturing commutators for small-size electric machines, which includes the steps of press forming a flanged hollow cylindrical workpiece, which has a flange at one end and is made of a conducting material, with outward protuberances defining corresponding inner recesses or cavities along a portion of the workpiece adjacent the flange, press forming the resultant workpiece into an axially grooved, flanged hollow body having eventual commutator segment portions and outward bridge portions bridging adjacent commutator segment portions, forming inner nails on the resultant body at positions corresponding to the respective commutator segment portions, mold filling an insulating material in the resultant nailed body, and diestamping connection hooks from the flange while at the same time removing the outward protuberances.

United States Patent [191 Yamaguchi 1 Feb. 27, 1973 [75] Inventor:

[73] Assignee: Nippondenso Kabushiki Kaisha,

Terumoto Yamaguchi, Anjo, Japan Aichi-ken, Japan [22] Filed: v Jan. 5,1971 [21] Appl. No.: 104,074

[30] Foreign Application Priority Data Primary Examiner-Richard J.Herbst Assistant Examiner-Carl E. Hall Attorney-Cushman, Darby & Cushman[57] ABSTRACT A method of manufacturing commutators for smallsizeelectric machines, which includes the steps of press forming a flangedhollow cylindrical workpiece, which has a flange at one end and is madeof a conducting material, with outward protuberances definingcorresponding inner recesses or cavities along a portion of theworkpiece adjacent the flange, press forming the resultant workpieceinto an axially grooved, flanged hollow body having eventual commutatorsegment portions and outward bridge portions bridging adjacentcommutator segment portions, forming inner nails on the resultant bodyat positions corresponding to the respective commutator segmentportions, mold filling an insulating material in the resultant nailedbody, and die-stamping connection hooks from the flange while at thesame time removing the outward protuberances.

1 Claim, 19 Drawing Figures PATENTEUFEB27|975 3,717. 928

sum 10F 3 Bvd gy aw ATTORNEY3 PATENTEDFEBZYIW 3,717. 928 SHEET 2 OF 3INVENTOR YO W W ATTORNEY S PATENTED 3. 7 l 7, 928

SHEET 3 OF 3 IN VENTOR METHOD OF MANUFACTURING COMMUTATORS FORSMALL-SIZE ELECTRIC MACHINES BACKGROUND OF THE INVENTION pre-shaped ringbody, fitting the resultant ring body on the armature shaft, thenmachining the periphery of the ring body to the end to prevent thevibration of the brushes, and finally splitting the machined ring bodyinto a required number of mutually insulated commutator segments bycutting the corresponding number of axial grooves across the thicknessof the ring body. This method requires special equipment and extra stepsfor cutting the axial grooves to split the ring body into the commutatorsegments, which is a significant disadvantage in respect ofproductivity.

To facilitate the process of cutting the axial grooves splitting thering body into the commutator segments after machining the ring body, itis the usual practice to pre-form appropriate slots or notches in theworkpiece in the afore-said pre-shaping step adjacent the end of theworkpiece and hence eventual commutator nearer the armature core inalignment with the axial grooves to be subsequently cut. This measure istaken particularly when the armature is small in size. Where thedistance between the armature core and the commuta- SUMMARY OF THEINVENTION An object of the invention is to provide a method ofmanufacturing commutators for revolving-armature type electric machines,in which the steps for cutting axial grooves in the workpiece to definesplitted commutator segments are dispensed with.

Another object of the invention is to provide a method of manufacturingcommutators, in which the mold filling of an insulating material in theeventual commutator is free from the adherence of the insulatingmaterial to the outer surface of the eventual commutator segments andconnection hooks.

According to the invention, the above ends are achieved by press forminga flanged hollow cylindrical workpiece, which has a flange at one endand is made of a conducting material, 'with outward protuberancesdefining corresponding inner recesses along a portion of the workpieceadjacent the flange, press forming, for

instance squeezing, the resultant workpiece into an axially grooved,flanged hollow body having commutator segment portions and outwardbridge portions bridging adjacent commutator segment portions, formingthe resultant body with inner nails at positions corresponding to therespective commutator segment portions, mold filling an insulatingmaterial in the resultant nailed body, and die-stamping connection hooksfrom the flange while removing the outward protuberances, wherebyexcellent commutators with high production efficiency are obtained.

One feature of the invention resides in that the axially grooved andnailed hollow body may be split into a required number of portionsconstituting the commutator segments in machining the body to remove thebridge portions, for instance after fitting the body with the insulationon the armature shaft, so that the undercut is required only to such anextent that a slight superficial part of the insulation between theadjacent commutator segments is removed. As the depth of cut is slight,a cutter with a thin cutter blade may be used without causing damagethereto. Also, the undercutting operation may be carried out at anextremely high speed.

Another feature of the invention resides in that the undesired adheringof the insulating material to the outer surfaces of the eventualcommutator segments are connection hooks is prevented from resultingduring the step of mold filling the insulating material in the axiallygrooved and nailed hollow body, since the flanged hollow cylindricalworkpiece of a conducting material is not formed with slots, but isformed with outward protuberances defining corresponding inner recessesprior to converting the resultant workpiece into the axially grooved,flanged hollow body having eventual commutator segment portions andoutward bridge portions by such means as squeezing or percussionpunching and form the resultant grooved body with inner nails and theprotuberances are removed at the time of die-stamping the connectionhooks from the flange after mold filling the insulating material in theaxially grooved and nailed hollow body. Thus, clear and excellentcommutators may be obtained. Also, as the step of removing theinsulating material adhered to the outer surfaces of the conductingparts of the even tual commutator as in the conventional method is notinvolved, much time and labor can be saved to improve productivity.

Furthennore, the formation of the protuberances to define thecorresponding recesses and the formation of bridge portions to definethe corresponding grooves arev achieved in separate steps, because thepress forming the protuberances and recesses in the portion of theworkpiece adjacent the flange, in which comparatively heavy pressure isrequired to deform the material, requires a punch and die block having acomparatively great mechanical strength, while the bridge portions andgrooves can be press formed in the remaining portion with a punch anddie block having a comparatively small mechanical strength, withoutcausing damage thereto. Also, the deformation of the flange during thesqueezing step as in the conventional method can be prevented.

3 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of arotary armature having a commutator manufactured according to theinvention.

FIGS. 2 through 19 illustrate one embodiment of the method according tothe invention, in which:

FIG. 2 is an end view showing a flanged hollow cylindrical workpieceformed with outward protuberances defining corresponding inner recesses;I

. FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a fragmentary sectional view, to an enlarged scale, takenalong line IV-IV in FIG. 3; I

FIG. 5 is a fragmentary sectional view, to an enlarged scale, showing aportion indicated at A in FIG. 3;

FIG. 6 is an end view showing an axially grooved, flanged hollow bodyhaving eventual commutator segment portions and outward bridge portions,which is obtained by squeezing the flanged hollow cylindrical workpieceformed with the outward protuberances and inner recesses shown in FIG.2;

FIG. 7 is a sectional view taken along line VII-VII in FIG. 6;

FIG. 8 is a fragmentary sectional view, on an enlarged scale, takenalong line VIII-VIII in FIG. 7;

FIG. 9 is a fragmentary sectional view, on an enlarged scale, showing aportion indicated at B in FIG. 7;

FIG. 10 is a fragmentary sectional view, on an enlarged scale, takenalong line X-X in FIG. 7;

FIG. 11 is an end view showing the axially grooved,

' flanged hollow body of FIG. 6 provided with amolding of an insulatingmaterial;

FIG. 12 is a sectional view taken along line XII-XII in FIG. 11;

FIG. 13 is an end view showing an axially grooved hollow body withconnection hooks and without the protuberances;

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will now bedescribed in conjunction with a preferred embodiment thereof withreference to the accompanying drawing.

The starting workpiece is made of a conducting material such as copperand has a flanged, hollow cylindrical configuration.

As shown in FIGS. 2 and 3, the workpiece is press formed with outwardprotuberances -2 defining corresponding inner recesses 1 along a portionof the workpiece adjacent a flange 3. As clearly shown in FIGS. 4 and 5,the margin of the protuberance 2 integral with the main portion 4 andflange 3 of the workpiece defines a narrow part not too narrow to causecracks at the time mold filling an insulating material to be describedlater.

Then, the resultant workpiece is squeezed (or percussion pressed) intoan axially grooved, flanged hollow body with outward bridge portion 6bridging adjacent eventual commutator segment portions and corresponding inner axial grooves 6' as generally indicated at X in FIGS. 6and 7. FIGS. 8 to 10 show in detail the outward bridge portion 6bridging adjacent eventual commutator segment portions and thecorresponding inner axial groove 6'.

Subsequently, inner nails 5 as indicated by dotted lines in FIG. 7 areformed on the resultant body at upper and lower positions for therespective commutator segment portions.

Thereafter, the resultant body having inner nails 5 is filled with aninsulating material by using a mold having a required configuration, asshown in FIG. 11 and 12. In the Figures, numeral 7 designates theinsulator molding having a shaft insertion bore 8. At this time, theprotuberances 2 prevents the insulating material 7 filled in the innerrecesses 1 from migrating therethrough and adhering to'the outersurfaces of the commutator segment portions and the flange 3. The innernails 5 are entirely embedded in the insulating material 7.

Afterwards, connection hooks 9 are formed by diestamping the flange 3 ofthe flanged body, as shown in FIGS. 13 and 14. By the die-stampingoperation, the outward protuberances 2 are removed at the same time. Asthe protuberances 2 defining a narrow part with the integral mainportion 4 of the body is integral with the flange 3 as mentionedearlier, they are removed integrally with the stamp-out portion 30, asshown in FIGS. 17 and-18.

Finally, the resultant hollow body filled with the insulating material 7and deprived of the outward protuberances 2 is machined to complete thecommutator, as shown in FIGS. 15 and 19. At this time, the outwardbridge portions 6 are cut away, so that the resultant commutatorsegments as indicated by Y in FIG. 19 are isolated by the insulatingmaterial filled in the previous inner axial grooves 6'.

Actually, the machining of the periphery of the hollow body filled withthe insulating material is carried out after fitting the body on thearmature shaft 11 such that the connection books 9 face the armaturecore, as shown in FIG. 1.

After the machining of the hollow body filled with the insulatingmaterial, grooves 12 (FIG. 1) are undercut in portions corresponding tothe previous 6 in FIG. 9 to slightly indent the surface of theinsulating material filled in the previous grooves 6 with respect to theperiphery of the commutator Y. This is. made because the copper segmentswear sooner than the insulating material. In case of using a punchhaving a diameter smaller than the diameter of the machined commutatorfor the formation of the outward bridge portions 6 and inner grooves 6',the bridge portions 6 are not completely removed and the commutatorsegment portions still remain integral with one another through thinnerbridges after the machining. In such case, the thinner bridgescorresponding to the inner piece adjacent the flange, converting theresultant workpiece into an axially grooved, flanged hollow body havingeventual commutator segment portions and outward bridge portionsdefining corresponding inner axial grooves and bridging adjacenteventual commutator segment portions, forming said axially grooved,flanged hollow body with inner nails at positions respectivelycorresponding to said eventual commutator segment portions, filling aninsulating material in the resultant nailed body, and die-stampingconnection hooks from said flange while simultaneously removing saidoutward protuberances.

is w r :i: a:

1. A method of manufacturing commutators for revolving-armature typeelectric machines comprising the steps of press forming a hollowcylindrical workpiece flanged at one end and made of a conductingmaterial with outward protuberances defining corresponding innerrecesses along a portion of said workpiece adjacent the flange,converting the resultant workpiece into an axially grooved, flangedhollow body having eventual commutator segment portions and outwardbridge portions defining corresponding inner axial grooves and bridgingadjacent eventual commutator segment portions, forming said axiallygrooved, flanged hollow body with inner nails at positions respectivelycorresponding to said eventual commutator segment portions, filling aninsulating material in the resultant nailed body, and die-stampingconnection hooks from said flange while simultaneously removing saidoutward protuberances.